Loud noise with older VSTi (Mystic etc) in C7 and C6

I have Cubase 6.5 and 7 currently running on Windows 7 64bit. This is a fresh installation.

Since a while, I noticed that I basically cannot use Mystic, D’Cota and other older Steinberg synths any more - instead of sound they just produce very loud noise that can only be stopped by switching off the plugin in the instrument rack.

This happens in both 32 and 64 bit Cubase. Any idea how to fix this?



Have you fixed it?